Patent GB-706063-A (GB)
Title: Improvements relating to systems for identifying railway vehicles
IPC: B61L25/04
Filed: 1952-01-08
Abstract: 706,063. Automatic train describers. GENERAL RAILWAY SIGNAL CO. Jan. 8, 1952 [Jan. 17, 1951], No. 607/52. Class 105 Automatic train describer apparatus comprises on the train one or more control coils each tuned to its respective frequency and, on the track a pick-up coil connected to the output of a frequency-sweep oscillation generator whose frequency recurrently sweeps through a range containing the frequencies of the control coils at least once during the inductive coupling when the control coils are passing the pick-up coil and controlled devices each actuated in simultaneous response to a respective one of said frequencies and to a variation in load on the oscillation generator due to the resonant coupling of a coil resonant at that frequency so that the combination of controlled devices actuated identifies the train. These train coils may be arranged to pass the pick-up coil simultaneously or in rapid succession. A voltage for actuating the controlled devices is derived dependent upon the rate-of-change of oscillator loadin gas the oscillator frequency sweeps through the frequency of the control coil(s) coupled to the pick-up coil. The operations of the controlled devices are arranged to transmit code signals to storage units of a typical train describer system, as for example, shown and described in U.S.A. Specification 2,184,702. The storage units are filled with the identity signals as successive trains pass the fixed location and, as the trains pass the point at which the identity information is used, the storage unit containing the corresponding identity information is restored to normal and the identity informations in other storage units are all moved up to the next storage unit in order. Fig. 3A shows the track apparatus at the approach to an interlocking area ; Fig..3B shows the apparatus at a control tower at the entrance to the interlocking area. The apparatus shown in Fig. 3B includes a display panel and storage units. The receiving, equipment, Fig. 3A includes a fixed pick-up coil 49 located adjacent the track rails which is fed with oscillations of for example 140 to 180 K.C., from a frequency sweep oscillator 44 of the Colpitt's type operating with a sweep frequency of 60 cycles per second and each train approaching the interlocking area has mounted upon it one or more tuned coils 50 each resonant at a different frequency. The coil 49 may be mounted above the track with its plane horizontal and the coils 50 mounted on the roof of the train in a horizontal plane so that they pass the coil 49 simultaneously or in succession. Alternatively the coil 49 may be mounted with its plane vertical as shown and alongside the track and the coils 50 are then mounted on the side of the train, stacked one above the other or arranged horizontally in line. When the train enters a short track section at the identifying location, a track relay TR1, Fig. 3A, is dropped away to condition the identifying and receiving equipment by connecting at its back contact 80 battery supply to the sweep range tuner 45 which is, for example, a motor driven variable capacity in the tuning circuit of the oscillator 44. A track relay TR2, Fig. 3B, at the entrance to the interlocking area drops away when the train enters that area to cancel the train designation storage. The loading effect on the oscillator 44 due to the presence of a coil 50 is only momentary and is made evident on the oscillator by a reduction in amplitude of the oscillations accompanied by a reduction in grid bias of an electron tube included in the oscillator 44 and is detected by a detector-amplifier 46 to provide a positive indication or presence signal which is applied to one control electrode of each of a plurality of control gas-filled tubes 54, e.g. thyratrons, one for each identifying frequency. A second signal which is indicative of the control frequency or position in the frequency sweep band at which the load on the oscillator 44 occurs is obtained from one of the tuned circuits 52 each tuned to its respective control frequency, all said circuits 52 being fed from the oscillator 44 so that such position signal is obtained as the oscillator 44 output sweeps through one of the control frequencies and is applied after amplification in amplifier 53 as a gating potential to another control grid of one of the thyratrons 54. The output signal from this thyratron is applied to a relay CR, e.g. CR1 in its plate circuit. The detector-amplifier 46 responds only to relatively rapid changes in the loading effect upon the oscillator and thus to the passage of a tuned circuit 50, but not to the passage of a metallic object past the pick-up coil 49. When the control thyratron 54 has been rendered conductive by the simultaneous application to its control grids of the presence and frequency position signals control by its control grid is lost and the tube can only be rendered non-conductive again by removal of the positive potential on its anode. To this end track repeater relay TPR, Fig. 3A on picking up in response to the dropping away of the track relay TR1 on a train approaching the identifying location, at its front contact 82 connects power through the windings of relays CR to the anodes of the thyratrons 54 and on dropping away relay TPR removes the power from the anodes of the thyratrons to render them non-conductive. As each train passes through the track section adjacent the identifying location one or more of the control relays CR1-CR4 is or are energized and at least one of the front contacts 84, 85, 86, 87 of the relays is closed, the code lines 135, 159, 160 and 182 being thereby selectively energized through the closed back contact 83 of the track relay TR1 and line 132 and causes the train identity code to be stored in the next available one of the storage units, Fig. 3B. When the train passes out of the track section relay TR1 picks up and at its open back contact 81 causes relay TPR to fall off to open at its front contact 82 the power supply circuit of the thyratrons 54 thereby rendering these tubes non-conductive and de-energizing all the control relays CR in readiness for selective operation on the passage of the next train past the pickup coil 49. In a modification in which the coils 50 on the train are arranged to pass the pick-up coil 49 in succession, the receiving equipment is adapted so that it will not register a train identity as complete if, for example, the train stops before all the train carried coils 50 have passed the pick-up coil 49. To this end a check relay is provided whose energizing winding is in the plate circuit of an additional gas discharge tube or thyratron with its shield grid connected directly to its cathode and is operated by the. presence signal from the detector-amplifier 46. The plate circuit of this tube also contains the secondary winding of a transformer whose primary winding is fed from an A.C. source so that the tube is only conductive on the positive half-cycles and when a presence signal is applied. The coils 50 are so mounted on the train that after the first has passed the coil 49, at all times one of the other coils 50 must be effectively coupled to the coil 49 until the last coil 50 has passed. Thus the check relay is intermittently energized as the coils 50 pass coil 49 and has quick pickup slow release characteristics. On picking up this relay completes an energizing circuit of a repeater relay which on picking-up de-energizes the delay line 133 during registration of the coil identity signals and both the check relay and its repeater relay maintain the energization of a relay for maintaining the power supply to the anodes of the thyratrons 54 and the control relays CR when any one of these is operated. When all the train coils 50 have passed the coil 49 the additional thyratron is no longer conductive in the absence of a presence signal so that the check relay and its repeater become de-energized but the repeater relay, having a slow release characteristic provides a momentary circuit for the selective energization of the code busbars 135, 159, 160, 182 dependent upon the control relays CR operated to energize a storage unit. On dropping away of the check repeater relay the apparatus is returned to normal and a positive potential is applied to the line 133 to isolate the storage unit so that it is fully independent and unresponsive to the registration of another train description registered in the receiving equipment. The dropping away of track relay TR2 Fig. 3B causes the energization of relay TPB which can also be energized by operation of cancel key ECB, to remove, at its contact 156 energy from the conductor 88 of the stick circuit of all the designation storage relays included in the No. 1 storage unit. These designation storage relays drop away thereby cancelling the train identity code stored in this unit. The picking up of relay TPB at its front contact 243 energizes relay TPC which on picking up applies energy at its front contact 245 to the conductor 88 and the stick circuits of the various designation storage relays in storage unit No. 1 ready for receiving the stored code from unit No. 2.